This invention relates to apparatus for removing or stripping tubes completely from a heat exchanger, condenser, boiler or the like.
2. Description of the Prior Art
Various tools have been suggested for forcibly extracting the expanded portions of tubes from their tube sheet holes. One such tube extractor is described in my copending application for Letters Patent for Tube Extractor, Ser. No. 950,276, filed Oct. 11, 1978, now U.S. Pat. No. 4,213,239. In that application an hydraulically activated broach is inserted into the tube end, expanded into cutting engagement with the inside diameter of the tube by a conically pointed mandrel within the broach, and then withdrawn, bringing the tube with it. The stroke of the this tool is a few inches, which is sufficient since the expanded portion does not often exceed this distance. After initiating the withdrawal of the tube with this or any other desired structure more rapidly acting equipment for further tube removal is desirable.
Lassarat, in U.S. Pat. No. 4,095,335, describes an automatic tube puller having a mandrel which is first threaded into the end of a tube. An hydraulic cylinder with a central bore is manually fitted around the mandrel, which it then grips with an external collet. The cylinder must apply sufficient force to break the expanded joint on the first stroke, that is, several tons. On subsequent strokes the collet will work its way up the mandrel and onto the tube, finally removing the tube completely from the exchanger. While the Lassarat tube puller is versatile in that it performs both extraction and removal of a tube, this structure is slow in operation and subject to other limitations. Insertion of the mandrel, fitting on the cylinder, and taking the first stroke to break the joint takes considerable time and does not compare favorably with other automatic tube extractors for this type of operation. In the removal phase it is also slow because of the many strokes that must be taken and because the piston must return to the front of the cylinder between strokes. The inherent low speed-high power characteristics of the Lassarat apparatus while necessary for initially extracting the tube, are not necessary for further removal.
Crawley and Ohmstede, in U.S. Pat. No. 4,125,928, describe an hydraulically reciprocable gripping and stacking device, fitted into a stationary framework, to which the exchanger must be attached after the shell has been removed. While suitable in some instances, the requirement that the exchanger be completely dismantled, the tube sheets and shell removed, and the tube bundle set up in the frame are serious drawbacks. This apparatus is not intended to remove tubes through tube sheets holes of an exchanger in situ.